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Tornado Shelters, More Important than Ever

While there isn’t a long-term trend in the number of U.S. tornadoes stronger than EF0, several recent studies suggest the time distribution of those tornadoes and their tendency to cluster in outbreaks may be changing. And more activity means having a plan in place to survive a storm is more important than ever. And luckily, tornado shelters are less expensive and easier to install than in years past.

EF1 Tornado Days and Active Tornado Days

Fewer Tornado Days, But More Active Days

When eliminating EF0 tornadoes from yearly counts, which have steadily risen over the past few decades due to more extensive spotter networks, the implementation of Doppler radar, and advanced technology such as smartphones and social media, there is essentially no long-term yearly trend in the raw number of EF1 and stronger tornadoes.

However, the number of days with at least one EF1+ tornado in the U.S. has fallen from an average of 150 such days in the early 1970s to around 100 days in the first decade of the 21st century, according to an October 2014 study in the journal Science.

However, the study by noted tornado researchers Dr. Harold Brooks of the National Severe Storms Laboratory, Greg Carbin of NOAA’s Storm Prediction Center, and Dr. Patrick Marsh, also of NOAA/SPC, found the number of days with a large number of tornadoes is actually increasing over time.

“The frequency of days with more than 30 EF1+ (tornadoes) has increased from 0.5 to 1 days per year in the 1960s and 1970s to 3 days per year over the past decade,” says the Brooks et al. study.

In essence, we have fewer days with tornadoes, but are packing more of them into the days we have. “Approximately 20 percent of the annual tornadoes in the most recent decade have occurred on the three biggest days of each year,” says the Brooks et al. study. So knowing what to do when severe weather strikes, and ideally, having a residential storm shelter, a community storm shelter easily accessible in your city, or a corporate storm shelter or commercial tornado shelter at your business or school is more important than ever.

Another recent study by Dr. James Elsner not only found a similar clustering of tornadoes into fewer days, but also a spatial clustering of tornadoes on those very active days.

“It appears that the risk of big tornado days with densely concentrated clusters of tornadoes is increasing,” Elsner says in the July 2014 study.
Large Swings in Monthly, Yearly Numbers

These clusters cause more damage in a defined area. So instead of being concerned about a single rotation, and potentially feeling relieved after a tornado passes, it is extremely important to be more vigilant and aware of other tornadoes in the area. Residential tornado shelters and community storm shelters are the best option to protect yourself from these unpredictable storms.

For only the second time since 1950, the first three weeks of March 2015 passed without a single tornado anywhere in the U.S.
Yet as recently as 2011, almost 1,700 tornadoes ripped across the nation, including 349 tornadoes in a four-day outbreak from April 25-28, the costliest tornado outbreak in U.S. history.

While year-to-year variability has long been prevalent in U.S. tornado counts, a 2014 study by Dr. Michael Tippett found volatility, a term he uses for variability in tornado counts, has increased since 2000.

Furthermore, the Brooks et al. study found the tendency for more monthly extreme highs and lows in EF1+ tornado counts in recent years.

“Excluding the zero-tornado months, there are more extreme months in the most recent 15 years of the database (1999-2013) than in the first 45 years,” says Brooks et al. 2014.

In other words, we’ve seen extreme high monthly tornado counts (758 tornadoes in April 2011, for example) and extreme low monthly tornado counts (March 2015, for example) more often over the past 15 years, a trend that may continue.

Of course, low tornado count years do not preclude significant tornadoes or tornado outbreaks. Despite the lowest three-year tornado count on record from 2012-2014, we still had destructive outbreaks in March 2012, in May 2013 (Moore and El Reno, Oklahoma), and April 2014 (Vilonia, Arkansas).

When Tornado Season Shifts Into Gear, Skewing Earlier in the Year-The Time to Install an Above Ground Tornado Shelter is NOW

Tornadoes can occur any time of year the overlap of sufficient moisture, atmospheric instability — relatively cold, dry air aloft overlying warm, humid air near the Earth’s surface — and a strong source of lift such as a warm front, dryline, strong jet-stream disturbance occur.

Because of that, it’s difficult to define a tornado season on a national scale as distinctly as, say, a hurricane season.

However, Brooks et al. tracked as a metric the occurrence of the year’s 50th EF1+ tornado to get a sense of whether the timing of the ramp-up in U.S. tornadoes typically seen in spring is changing.

While the long-term average date (March 22) hasn’t changed, Brooks et al. found a marked increase in the number of “late-start” and “early-start” years since the late 1990s. The four latest starts and five of the ten earliest starts to the season all occurred in the 1999-2013 period. These range from late January (1999 and 2008) to late April (2002, 2003, 2004 and 2010).

In essence, even the date the season kicks into a higher gear is becoming more volatile-so don’t wait to install your tornado shelter.

Climate Change Role?

Now, the toughest question: Is climate change playing a role in the increasing variability of the nation’s tornadoes?

The short answer is, possibly.

The challenge in answering this question is linking short-fuse events like tornadoes and tornado outbreaks to long-term changes in atmospheric parameters generally conducive for severe thunderstorms, such as instability and wind shear.

Studies by Dr. Jeff Trapp and Dr. Noah Diffenbaugh, among others, suggest atmospheric instability, driven by increased moisture, is expected to be greater in a warming climate. However, wind shear, crucial for the formation of supercells which can produce the strongest tornadoes, may diminish overall, but may feature more days with higher wind shear.

Therefore, the overall environment may be more conducive for severe thunderstorms (with large hail and damaging winds), but it remains unclear whether the number of tornadoes or even strong tornadoes would necessarily rise in a warming world.

This brings up an interesting possibility, a seasonal outlook for severe weather, similar to hurricane season outlooks.
“I suspect that ultimately knowing if a severe weather season will be above, below, or near normal would be important for reinsurance portfolios as an increasing amount of money is spent on hail and wind claims,” said Dr. Patrick Marsh from NOAA/SPC.

The best advice is don’t think that you can predict the severity of tornado season or even when it begins, and definitely do not wait until after a storm strikes to realize the need to purchase a storm shelter. Tornado shelters of all sizes are more affordable than ever and Safe-T-Shelter even partners with local credit unions for financing. Everyone deserves the right to protect their family from unpredictable storms. So whether it is a residential storm shelter, a community storm shelter, a commercial storm shelter or a corporate storm shelter, Safe-T-Shelter can help, and our 20+ years experience means you can have confidence in our products and our longevity.

Tornado Safety Questions and Answers

(beneath the video below)

Storm Shelters, Safe Rooms, and Tornado Shelters

A reinforced safe room (or above-ground tornado shelter) is as good as an underground shelter. Residential Safe rooms are specially-designed reinforced tornado shelters built into homes, schools and other buildings. The Federal Emergency Management Agency (or FEMA), in close cooperation with experts in wind engineering and tornado damage, has developed detailed guidelines for constructing a safe room and the storm shelters built by Safe-T-Shelter meet or exceed those specifications.

A tornado watch defines a cluster of counties where tornadoes and other kinds of severe weather are possible in the next several hours. It does not mean tornadoes are imminent, just that you need to be alert, and to be prepared to go to safe shelter if tornadoes do happen or a warning is issued. This is the time to turn on local TV or radio, turn on and set the alarm switch on your weather radio, make sure you have ready access to safe shelter, and make your friends and family aware of the potential for tornadoes in the area. The Storm Prediction Center issues tornado and severe thunderstorm watches; here is an example.

What is a tornado warning?

A tornado warning means that a tornado has been spotted, or that Doppler radar indicates a thunderstorm circulation which can spawn a tornado. When a tornado warning is issued for your town or county, take immediate safety precautions. local NWS offices issue tornado warnings.

Do mobile homes attract tornadoes?

Of course not. It may seem that way, considering most tornado deaths occur in them, and that some of the most graphic reports of tornado damage come from mobile home communities. The reason for this is that mobile homes are, in general, much easier for a tornado to damage and destroy than well-built houses and office buildings. A brief, relatively weak tornado which may have gone undetected in the wilderness, or misclassified as severe straight-line thunderstorm winds while doing minor damage to sturdy houses, can blow a mobile home apart. Historically, mobile home parks have been reliable indicators, not attractors, of tornadoes. Mobile home communities are also great places for our community shelters to be installed. If you live in a mobile home community, please tell the owner of the mobile home park to contact Safe-T-Shelter through our website www.stormshelter.com for a free cost estimate for a community shelter.

Long ago, I was told to open windows to equalize pressure. Now I have heard that’s a bad thing to do. Which is right?

Opening the windows is absolutely useless, a waste of precious time, and can be very dangerous. Don’t do it. You may be injured by flying glass trying to do it. And if the tornado hits your home, it will blast the windows open anyway.

I’ve seen a video of people running under a bridge to ride out a tornado. Is that safe?

Absolutely not! Stopping under a bridge to take shelter from a tornado is a very dangerous idea, for several reasons:

Deadly flying debris can still be blasted into the spaces between bridge and grade, and impaled in any people hiding there.
Even when strongly gripping the girders (if they exist), people may be blown loose, out from under the bridge and into the open–possibly well up into the tornado itself. Chances for survival are not good if that happens.
The bridge itself may fail, peeling apart and creating large flying objects, or even collapsing down onto people underneath. The structural integrity of many bridges in tornado winds is unknown–even for those which may look sturdy.
Whether or not the tornado hits, parking on traffic lanes is illegal and dangerous to yourself and others. It creates a potentially deadly hazard for others, who may plow into your vehicle at full highway speeds in the rain, hail, and/or dust.
Also, it can trap people in the storm’s path against their will, or block emergency vehicles from saving lives.
The people in that infamous video were extremely fortunate not to have been hurt or killed. They were actually not inside the tornado vortex itself, but instead in a surface inflow jet–a small belt of intense wind flowing into the base of the tornado a few dozen yards to their south. Even then, flying debris could have caused serious injury or death. More recently, on 3 May 1999, two people were killed and several others injured outdoors in Newcastle and Moore OK, when a violent tornado blew them out from under bridges on I-44 and I-35. Another person was killed that night in his truck, which was parked under a bridge. For more information, meteorologist Dan Miller of NWS Duluth has assembled an online slide presentation about this problem.

So if I’m in a car, which is supposed to be very unsafe, and shouldn’t get under a bridge, what can I do?

Vehicles are notorious as death traps in tornadoes, because they are easily tossed and destroyed. Either leave the vehicle for sturdy shelter or drive out of the tornado’s path. When the traffic is jammed or the tornado is bearing down on you at close range, your only option may be to park safely off the traffic lanes, get out and find a sturdy building for shelter, if possible. If not, lie flat in a low spot, as far from the road as possible (to avoid flying vehicles). However, in open country, the best option is to escape if the tornado is far away. If the traffic allows, and the tornado is distant, you probably have time to drive out of its path. Watch the tornado closely for a few seconds compared to a fixed object in the foreground (such as a tree, pole, or other landmark). If it appears to be moving to your right or left, it is not moving toward you. Still, you should escape at right angles to its track: to your right if it is moving to your left, and vice versa–just to put more distance between you and its path. If the tornado appears to stay in the same place, growing larger or getting closer–but not moving either right or left–it is headed right at you. You must take shelter away from the car or get out of its way fast! If the tornado starts to hit your car, get as low as you can while staying in your seatbelt, leaning down and away from the windows and windshield as far as possible.

I have a basement, and my friend said to go to the southwest corner in a tornado. Is that good?

Not necessarily. The SW corner is no safer than any other part of the basement, because walls, floors and furniture can collapse (or be blown) into any corner. The “safe southwest corner” is an old myth based on the belief that, since tornadoes usually come from the SW, debris will preferentially fall into the NE side of the basement. There are several problems with this concept, including:

Tornadoes are mostly circular, so the damaging wind may blow from any direction; and
Tornadoes themselves may arrive from any direction.
In a basement, the safest place is under a sturdy workbench, mattress or other such protection–and out from under heavy furniture or appliances resting on top of the floor above.

What is a safe room?

So-called “safe rooms” are reinforced small rooms built in the interior of a home, fortified by concrete and/or steel to offer extra protection against tornadoes, hurricanes and other severe windstorms. They can be built in a basement, or if no basement is available, on the ground floor. In existing homes, interior bathrooms or closets can be fortified into “safe rooms” also. FEMA has more details online. Those who have safe rooms, or any other kind of tornado shelter, should register them with the local fire department to help with rescue in case the entrance(s) are blocked by debris. If your home does not have a residential storm shelter or safe room, contact us for a free quote. We also offer low or no interest financing if needed to ensure all those that would like to protect themselves from a potential storm, are able to do so. You can contact us through our website here (www.stormshelter.com) or at our local or 800# listed above at the top of each page.

How can building codes help, or hurt, tornado safety?

Building codes vary greatly across the country, not only from state to state but even from place to place in one county. Codes also have changed over time so that different ages of housing stock in the same community can have different legal standards of strength. Enforcement of codes also can be highly variable, both over time and from place to place. Even the strictest codes won’t help without rigorous enforcement. The bottom line: if you buy an existing house or business structure, you cannot fully know its tornado resistance without knocking holes in wall paneling and exposing areas such as wall-foundation attachments, wall-roof connections and (for multi-story structures) internal attachments from one level to another. The best bet for existing stock may be to retrofit or add on a tornado shelter of some sort, depending on your needs and finances. For new construction, the most tornado-ready codes require, among other things: anchor bolts with nuts and washers attached (connecting foundation to floor plate), strong ties (a.k.a. hurricane clips) connecting floor plate to wall studs and wall studs to roof, and use of straight nails or screws for other connections, not cut nails. If you are considering new construction, please check with your local building-regulation agency, demand above-code work to the level you can afford, and directly monitor your builder’s subcontractors at those crucial early stages to ensure compliance with your own higher standards. NIST has recommended raising standards nationwide, based on their study of the Joplin tornado from 2011.

What about community tornado shelters?

Community tornado shelters are excellent ideas for apartment complexes, schools, mobile home parks, factories, office complexes and other facilities where large groups of people live, work or study. FEMA has some excellent design and construction guidance for these kinds of shelters; and a licensed engineer can help customize them to the needs of your facility. We offer community storm shelters for businesses, or communities alike. If you are interested in a no obligation cost estimate, please contact us here through our website, or call us during normal business hours. With over 21 years of experience, and our shelters surviving many direct hits with 0 fatalities, you can count on our product and the quality of our service. We would love to help keep you and your community or business safe. We have custom and prefab tornado shelters for sale of all sizes.

What about tornado safety in sports stadiums or outdoor festivals?

Excellent question–and a very, very disturbing one to many meteorologists and event planners. Tornadoes have passed close to such gatherings on a few occasions, including a horse race in Omaha on 6 May 1975 and a crowded dog track in West Memphis AR on 14 December 1987. A supercell without a tornado hit a riverside festival in Ft. Worth in 1995, catching over 10,000 people outdoors and bashing many of them with hail bigger than baseballs. Tornadoes have hit the football stadium for the NFL Tennessee Titans, and the basketball arena for the NBA Utah Jazz. Fortunately, they were both nearly empty of people at the time. There is the potential for massive death tolls if a stadium or fairground is hit by a tornado during a concert, festival or sporting event, even with a warning in effect. Fans may never know about the warning; and even if they do, mass disorder could result in casualties even if the tornado doesn’t hit. Stadium, race track and festival managers should work with local emergency management officials to develop a plan for tornado emergencies–both for crowd safety during the watch and warning stages, and (similar to a terrorism plan) for dealing with mass casualties after the tornado.

I am a school administrator, and I don’t know where to start with developing a safety plan. Can you help?

Gladly. Every school is different, so a safety plan which works fine for one may not be well-suited for another. There is a website with preparedness tips for school administrators which can provide helpful tips in devising a safety plan. These strategies can be adapted for nursing homes, dorms, barracks and similar structures as well. Please contact us for a free no obligation cost estimate to provide you with a community storm shelter to protect your school (business, or community). With over 21 years of experience and with many direct hits to our shelters, we have never had a failure or a lost life. We would love to help you ensure the safety of all people in your school (business or community) when the next storm strikes.

I am seeking advice to protect employees in a large, one-story commercial building that has pre-poured cement outer walls and a metal roof. We have no basement, the interior offices are drywall partitions with a dropped ceiling and there does not appear to be any area that is secure. The local fire department has no suggestions.

This manner of construction is very common; however, it’s hard to know the integrity of any particular building without an engineering analysis, preferably by hiring a specialist with experience in wind engineering. My experience doing damage surveys is that large-span, pre-fab, concrete and metal beam buildings are sturdy up to a “failure point”–which can vary a lot from site to site–but then crumple quickly and violently once that threshold is reached. A concrete-lined (and -topped) safe room with no windows is recommended. This is an emergency bunker that may double as a restroom, break room or employee lounge, but should be big enough to fit all occupants in the event of a warning. For more information on safe rooms, see FEMA’s safe room page, which deals mainly with residential construction, but which can be adapted for office use. FEMA also has posted a page on in-hospital shelter in Kansas, that may be useful for this purpose also. The Wind Engineering Research Center at Texas Tech University also provides guidance about shelters. The insulated concrete form (ICF) is a very wind- and debris-resistant construction method for many small buildings or additions, whether doing new construction or retrofitting. But the best course of action is to contact us for a free no obligation cost estimate to supply your business with a custom tornado shelter to protect your employees from an unpredictable storm. We offer storm shelters and safe rooms to protect a single person or 500+. We can customize our offerings to your exact needs because we build them in our facility. We are not a reseller and that leads to cost savings and more peace of mind due to the transparency of our operations and our reputation that has been built over more than 21 years in business protecting people from dangerous tornadoes.

What would happen if a large, violent tornado hit a major city today?

This has happened on several occasions, including in parts of Oklahoma City on 3 May 1999 and Birmingham on 27 April 2011. Because of excellent, timely watches and warnings and intense media coverage of the Oklahoma tornado long before it hit, only 36 people were killed. The damage toll exceeded $1 billion. Still, it did not strike downtown, and passed over many miles of undeveloped land. Moving the same path north or south in the same area may have led to much greater death and damage tolls. The threat exists for a far worse disaster! Placing the same tornado outbreak in the Dallas-Ft. Worth Metroplex, especially during rush hour gridlock (with up to 62,000 vehicles stuck in the path), the damage could triple what was done in Oklahoma. There could be staggering death tolls in the hundreds or thousands, devastated infrastructure, overwhelmed emergency services, and massive amounts of rubble requiring months of cleanup. Ponder the prospect of such a tornado’s path in downtown Dallas, for example. The North Texas Council of Governments and NWS Ft. Worth has compiled a very detailed study of several such violent tornado disaster scenarios in the Metroplex, which could be adapted to other major metro areas as well.

Could we have some sort of alert system where a computer automatically calls people in a tornado warning to let them know they could be in danger?

This idea has some merit. Right now, though, there are several logistical problems. First, a tornado may take out phone lines, or the power to run them. Barring that, the phone network reaches saturation pretty easily if someone (or something) tries to try to dial thousands of numbers at once. Finally, people would need to be patient and willing to accept a majority of false alarm calls. Most tornado warnings do not contain tornadoes, because of the uncertainties built into tornado detection which we can’t yet help. And even when a tornado happens, it usually hits only a tiny fraction of the warned area (again, because of forecasting uncertainties); so most people called by the automated system would not be directly hit.

Are there smartphone apps that offer warnings for tornadoes and other kinds of dangerous weather?

Yes, private companies have developed several apps that relay NWS tornado warnings to smartphones, based on their location and/or user-specified places. For example, you can set some apps to always provide warnings for certain ZIP codes or addresses of interest away from your current location, such as those of your home, business, or friends and loved ones. We cannot endorse any particular apps, but a search in your device provider’s app store should yield some that are highly rated, along with reviews by users. NOAA has partnered with major cellular providers to push “Wireless Emergency Alerts” to most modern cell phones, and those include tornado warnings. Also, some local governments have enacted warning-alert systems that alarm phones in their jurisdictions when warnings are issued. Please check with your local emergency management agency to see if such a system is in place in your area, or soon will be. Caution: cell-phone warnings cannot work if the phone system is disabled, and might fail or be delayed if the network is overloaded (as can happen during a major storm or other disaster).

I recently moved from the Plains and noticed that there are no “tornado warning” sirens here. Is this because tornadoes don’t occur here? Isn’t it required to have sirens everywhere?

There is no nationwide requirement for tornado sirens. Siren policy is local and varies from place to place. The National Weather Service has no control over sirens or siren policy. The NWS issues watches and warnings; but it is up to the local governments to have a community readiness system in place for their citizens. In conversations with emergency managers and spotter coordinators, I have found that the two most common reasons for a lack of sirens are low budgets and the misconception that tornadoes cannot happen in an area. Your city and/or county emergency manager would be the first person to query about the tornado preparedness program in your community. Remember: outdoor sirens are for outdoor use. Everyone should have ways to receive warnings besides sirens.

Our office would like to print signs (universal symbol image type signs) similar to “emergency exit,” “fire extinguisher,” etc. that could be used to identify designated tornado shelter areas. Can you provide me with a graphic or something I can use?

Sure! There isn’t a universal tornado shelter symbol yet. Any such sign should be very bold and noticeable–yet designed to be simple, with minimal visual clutter, so even a small child can recognize it. In response to this question, here is one possible tornado shelter sign which may be printed and used freely. There are also versions with arrows pointing right, left, up, and down. The signs ideally should be printed in color, on heavy card stock or sticker paper for durability.

Thanks for reading our Tornado Safety Questions and Answers and please contact us through our website if you are interested in exploring a tornado shelter for your home, business, or community.

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Aqua Marine Enterprises, Inc., manufacturer of Safe-T-Shelter® safe rooms, has been manufacturing and installing safety shelters since 1995. Our company's goal is the same since we began our operation -- safety.